James Whitbrook for Toybox i09 compiles a list of the most bizarre incarnations of Spider-Man, taking into account alternate universes, spinoffs and the like.
A shining example, pictured above, is the Spectacular Spider-Ham. First appearing on comic book pages in Marvel Tails Starring Peter Porker the Spectacular Spider-Ham, circa 1983, this porcine Spidey was found in Earth-8311, a universe of anthropomorphic animal superheroes. The invention of Mark Armstrong and Tom DeFalco, Peter Porker was bitten by radioactive animal scientist (Aunt) May Porker, which tranformed him into the porky power seen above.
Spider-Ham joined forces with Nick Furry, Captain Americat, and Hulk-Bunny and battled villains Ducktor Doom, Buzzard and Hog-Zilla, among others. According to Whitbrook, the Ham is one of the most popular alt-Spider-Men. Pigs don't have to fly before I understand why.
See more bizarre manifestations of Spider-Man here.